This disclosure relates to method for texturing polymeric films and to articles comprising these textured films.
Films manufactured from organic polymers (having glass transition temperatures of greater than or equal to about 130° C.) that have thicknesses of less than or equal to about 75 micrometers and large surface widths of greater than or equal to about 1,200 millimeters are generally difficult to manufacture without defects such as wrinkles, comets, veins, die lines, gel particles, particulate inclusions, or the like. Texturing films improves their appearance and minimizes the visibility of defects. Texturing the surfaces of such films improves the ability of the film to adhere to another surface, improves printability, reduces the visibility of surface scratches and the other aforementioned defects to one observing or inspecting the textured film.
Textured films are often manufactured via a solution based process, wherein the organic polymer is dissolved in a solvent to create a polymer solution. The polymer solution is then cast onto a smooth surface. Solvent is allowed to evaporate from the cast polymer solution. A doctor blade is drawn across the surface of the cast polymer solution to produce a film having a uniform thickness following which the surface is textured. The texturing afforded by this method occurs on only one surface of the film. This is an expensive process and has a negative environmental impact because of the presence of the solvent. Manufacturing textured films from the melt (molten state) is less expensive than those manufactured from solution, but the melt process is fraught with problems due to electrostatic charges that develop on the surface of the film that cause pinning of the film.
It is therefore desirable to develop a method to texture films having a thickness of less than or equal to about 100 micrometers when the films are manufactured from a molten state. It is also desirable to develop a textured film whose texture reduces the visibility of defects present in the film.